This model describes a family of predicted regulatory proteins with a conserved zinc finger/HTH architecture. The amino-terminal region contains a novel domain, featuring two CXXC motifs and occuring in a number of small bacterial proteins as well as in the present family. The carboxyl-terminal region consists of a helix-turn-helix domain, modeled by pfam01381. The predicted function is DNA binding and transcriptional regulation. Length = 127

Members of this family belong to a clade of helix-turn-helix DNA-binding proteins, among the larger family pfam01381 (HTH_3; Helix-turn-helix). Members are similar in sequence to the HipB protein of E. coli. Genes for members of the seed alignment for this protein family were found to be closely linked to genes encoding proteins related to HipA. The HibBA operon appears to have some features in common with toxin-antitoxin post-segregational killing systems.

They include the characterised member HigA, without which the killer protein HigB cannot be cloned. The hig (host inhibition of growth) system is noted to be unusual in that killer protein is encoded by the upstream member of the gene pair.; GO: 0003677 DNA binding.

This family consists of several phage CI repressor proteins and related bacterial sequences. The CI repressor is known to function as a transcriptional switch, determining whether transcription is lytic or lysogenic.

This includes a CRISPR-associated gene region in Geobacter sulfurreducens PCA, and plasmids in Agrobacterium tumefaciens and Coxiella burnetii. They are found together with mobile mystery protein B, a member of the Fic protein family (IPR003812 from INTERPRO). Mobile mystery protein A is encoded by the upstream member of the gene pair and contains a helix-turn-helix domain..

The gene is almost invariably the downstream member of a gene pair. It is a predicted DNA-binding protein from a clade within the helix-turn-helix family IPR001387 from INTERPRO. These gene pairs, when found on the bacterial chromosome, are located often with prophage regions, but also both in integrated plasmid regions and in housekeeping gene regions. Analysis suggests that the gene pair may serve as an addiction module..

The operators at which it binds vary considerably in DNA sequence and location within the promoter; when bound to the Trp operon it recognises the sequence 5'-ACTAGT-3' and acts to prevent the initiation of transcription. The TrpR controls the trpEDCBA (trpO) operon and the genes for trpR, aroH, mtr and aroL, which are involved in the biosynthesis and uptake of the amino acid tryptophan . The repressor binds to the operators only in the presence of L-tryptophan, thereby controlling the intracellular level of its effector; the complex also regulates Trp repressor biosynthesis by binding to its own regulatory region. TrpR acts as a dimer that is composed of identical 6-helical subunits, where four of the helices form the core of the protein and intertwine with the corresponding helices from the other subunit. This entry represents Trp repressors found in proteobacterial and chlamydial species.; GO: 0016564 transcription repressor activity, 0006355 regulation of transcription DNA-dependent.

Members of this family belong to a clade of helix-turn-helix DNA-binding proteins, among the larger family pfam01381 (HTH_3; Helix-turn-helix). Members are similar in sequence to the HipB protein of E. coli. Genes for members of the seed alignment for this protein family were found to be closely linked to genes encoding proteins related to HipA. The HibBA operon appears to have some features in common with toxin-antitoxin post-segregational killing systems.

This family consists of several phage CI repressor proteins and related bacterial sequences. The CI repressor is known to function as a transcriptional switch, determining whether transcription is lytic or lysogenic.

They include the characterised member HigA, without which the killer protein HigB cannot be cloned. The hig (host inhibition of growth) system is noted to be unusual in that killer protein is encoded by the upstream member of the gene pair.; GO: 0003677 DNA binding.

This includes a CRISPR-associated gene region in Geobacter sulfurreducens PCA, and plasmids in Agrobacterium tumefaciens and Coxiella burnetii. They are found together with mobile mystery protein B, a member of the Fic protein family (IPR003812 from INTERPRO). Mobile mystery protein A is encoded by the upstream member of the gene pair and contains a helix-turn-helix domain..

The gene is almost invariably the downstream member of a gene pair. It is a predicted DNA-binding protein from a clade within the helix-turn-helix family IPR001387 from INTERPRO. These gene pairs, when found on the bacterial chromosome, are located often with prophage regions, but also both in integrated plasmid regions and in housekeeping gene regions. Analysis suggests that the gene pair may serve as an addiction module..

This family consists of the N terminus of homeobox-containing transcription factor HNF-1. This region contains a dimerization sequence and an acidic region that may be involved in transcription activation. Mutations and the common Ala/Val 98 polymorphism in HNF-1 cause the type 3 form of maturity-onset diabetes of the young (MODY3).

This DNA binding domain is based on peptide fragmentation data. This domain is proximal to DNA in the promoter/holoenzyme complex. Furthermore this region contains a putative helix-turn-helix motif. At the C-terminus, there is a highly conserved region known as the RpoN box and is the signature of the sigma-54 proteins.

They alter the specificity of promoter recognition. Most bacteria express a multiplicity of sigma factors. Two of these factors, sigma- 70 (gene rpoD), generally known as the major or primary sigma factor, and sigma-54 (gene rpoN or ntrA) direct the transcription of a wide variety of genes. The other sigma factors, known as alternative sigma factors, are required for the transcription of specific subsets of genes. With regard to sequence similarity, sigma factors can be grouped into two classes: the sigma-54 and sigma-70 families. The sigma-70 family has many different sigma factors (see the relevant entry IPR000943 from INTERPRO). The sigma-54 family consists exclusively of sigma-54 factor , required for the transcription of promoters that have a characteristic -24 and -12 consensus recognition element but which are devoid of the typical -10, -35 sequences recognized by the major sigma factors. The sigma-54 factor is also characterised by its interaction with ATP-dependent positive regulatory proteins that bind to upstream activating sequences. Structurally sigma-54 factors consist of three distinct regions: A relatively well conserved N-terminal glutamine-rich region of about 50 residues that contains a potential leucine zipper motif. A region of variable length which is not well conserved. A well conserved C-terminal region of about 350 residues that contains a second potential leucine zipper, a potential DNA-binding 'helix-turn-helix' motif and a perfectly conserved octapeptide whose function is not known. ; GO: 0003677 DNA binding, 0003700 transcription factor activity, 0003899 DNA-directed RNA polymerase activity, 0016987 sigma factor activity, 0006352 transcription initiation, 0006355 regulation of transcription DNA-dependent.

Transcription initiation from promoter elements requires a sixth, dissociable subunit called a sigma factor, which reversibly associates with the core RNA polymerase complex to form a holoenzyme . RNA polymerase recruits alternative sigma factors as a means of switching on specific regulons. Most bacteria express a multiplicity of sigma factors. Two of these factors, sigma-70 (gene rpoD), generally known as the major or primary sigma factor, and sigma-54 (gene rpoN or ntrA) direct the transcription of a wide variety of genes. The other sigma factors, known as alternative sigma factors, are required for the transcription of specific subsets of genes. With regard to sequence similarity, sigma factors can be grouped into two classes, the sigma-54 and sigma-70 families. Sequence alignments of the sigma70 family members reveal four conserved regions that can be further divided into subregions eg. sub-region 2.2, which may be involved in the binding of the sigma factor to the core RNA polymerase; and sub-region 4.2, which seems to harbor a DNA-binding 'helix-turn-helix' motif involved in binding the conserved -35 region of promoters recognized by the major sigma factors , . Members of this entry represent RNA polymerase sigma factor F. Within the Firmicutes, Sigma-F is specifically, and universally, a component of the endospore formation program, and is expressed in the forespore to turn on the expression of dozens of genes. It is closely related to sigma-G, which is also expressed in the forespore.; GO: 0003677 DNA binding, 0003700 transcription factor activity, 0016987 sigma factor activity, 0006352 transcription initiation, 0006355 regulation of transcription DNA-dependent.

Transcription initiation from promoter elements requires a sixth, dissociable subunit called a sigma factor, which reversibly associates with the core RNA polymerase complex to form a holoenzyme . RNA polymerase recruits alternative sigma factors as a means of switching on specific regulons. Most bacteria express a multiplicity of sigma factors. Two of these factors, sigma-70 (gene rpoD), generally known as the major or primary sigma factor, and sigma-54 (gene rpoN or ntrA) direct the transcription of a wide variety of genes. The other sigma factors, known as alternative sigma factors, are required for the transcription of specific subsets of genes. With regard to sequence similarity, sigma factors can be grouped into two classes, the sigma-54 and sigma-70 families. Sequence alignments of the sigma70 family members reveal four conserved regions that can be further divided into subregions eg. sub-region 2.2, which may be involved in the binding of the sigma factor to the core RNA polymerase; and sub-region 4.2, which seems to harbor a DNA-binding 'helix-turn-helix' motif involved in binding the conserved -35 region of promoters recognized by the major sigma factors , . This group of similar sigma-70 factors includes clades found in Bacilli (including the sporulation factors SigF:IPR014236 from INTERPRO and SigG:IPR014212 from INTERPRO as well as SigB:IPR014288 from INTERPRO), and the high GC Gram-positive bacteria (Actinobacteria) where a variable number of them are found depending on the lineage.; GO: 0003677 DNA binding, 0003700 transcription factor activity, 0016987 sigma factor activity, 0006352 transcription initiation, 0006355 regulation of transcription DNA-dependent.

Transposase proteins are necessary for efficient DNA transposition. This family includes insertion sequences from Synechocystis PCC 6803 three of which are characterized as homologous to bacterial IS5- and IS4- and to several members of the IS630-Tc1-mariner superfamily.

>TIGR00673 cynS cyanate hydratase; InterPro: IPR008076 Cyanase, an enzyme found in bacteria and plants, catalyses the reaction of cyanate with bicarbonate to produce ammonia and carbon dioxide, allowing the host organisms to overcome the toxicity of environmental cyanate

The cyanate lyase monomer is composed of two domains: an N-terminal domain that shows structural similarity to the DNA-binding alpha-helix bundle motif, and a C-terminal domain that has an 'open fold' that shows no structural similarity to other proteins . The enzyme is active as a homodecamer of 17kDa subunits, and displays half-site binding of substrates or substrate analogues. The dimer structure reveals the C-terminal domains to be intertwined; the decamer is formed from a pentamer of these dimers. The active site of the enzyme is located between dimers and comprises residues from four adjacent subunits of the homodecamer. Synonym(s): cyanase lyase, cyanase hydrolase ; GO: 0016836 hydro-lyase activity, 0008152 metabolic process.

Putative helix-turn-helix (HTH) MerR-like transcription regulators (subgroup 5), N-terminal domain. Based on sequence similarity, these proteins are predicted to function as transcription regulators that mediate responses to stress in eubacteria. They belong to the MerR superfamily of transcription regulators that promote transcription of various stress regulons by reconfiguring the operator sequence located between the -35 and -10 promoter elements. A typical MerR regulator is comprised of two distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their N-terminal domains are homologous and contain a DNA-binding winged HTH motif, while the C-terminal domains are often dissimilar and bind specific coactivator molecules such as metal ions, drugs, and organic substrates.

The CUT domain is a DNA-binding motif which can bind independently or in cooperation with the homeodomain, often found downstream of the CUT domain. Multiple copies of the CUT domain can exist in one protein .

Proteins in this family mostly have a truncated helix-turn-helix (HTH) MerR-like domain. They lack a portion of the C-terminal region, called Wing 2 and the long dimerization helix that is typically present in MerR-like proteins. These truncated domains are found in response regulator receiver (REC) domain proteins (i.e., CheY), cytosine-C5 specific DNA methylases, IS607 transposase-like proteins, and RacA, a bacterial protein that anchors chromosomes to cell poles.

>TIGR02846 spore_sigmaK RNA polymerase sigma-K factor; InterPro: IPR014209 The bacterial core RNA polymerase complex, which consists of five subunits, is sufficient for transcription elongation and termination but is unable to initiate transcription

Transcription initiation from promoter elements requires a sixth, dissociable subunit called a sigma factor, which reversibly associates with the core RNA polymerase complex to form a holoenzyme . RNA polymerase recruits alternative sigma factors as a means of switching on specific regulons. Most bacteria express a multiplicity of sigma factors. Two of these factors, sigma-70 (gene rpoD), generally known as the major or primary sigma factor, and sigma-54 (gene rpoN or ntrA) direct the transcription of a wide variety of genes. The other sigma factors, known as alternative sigma factors, are required for the transcription of specific subsets of genes. With regard to sequence similarity, sigma factors can be grouped into two classes, the sigma-54 and sigma-70 families. Sequence alignments of the sigma70 family members reveal four conserved regions that can be further divided into subregions eg. sub-region 2.2, which may be involved in the binding of the sigma factor to the core RNA polymerase; and sub-region 4.2, which seems to harbor a DNA-binding 'helix-turn-helix' motif involved in binding the conserved -35 region of promoters recognized by the major sigma factors , . The sporulation-specific transcription factor sigma-K (also called sigma-27) is expressed in the mother cell compartment of endospore-forming bacteria such as Bacillus subtilis. Like its close homologue sigma-E (sigma-29, see IPR014200 from INTERPRO), also specific to the mother cell compartment, it must be activated by a proteolytic cleavage. Note: that in Bacillus subtilis (and apparently also in Clostridium tetani), but not in other endospore forming species such as Bacillus anthracis, the sigK gene is generated by a non-germline (mother cell only) chromosomal rearrangement that recombines coding regions for the N-terminal and C-terminal regions of sigma-K .; GO: 0003677 DNA binding, 0003700 transcription factor activity, 0016987 sigma factor activity, 0006352 transcription initiation, 0006355 regulation of transcription DNA-dependent.

Transcription initiation from promoter elements requires a sixth, dissociable subunit called a sigma factor, which reversibly associates with the core RNA polymerase complex to form a holoenzyme . RNA polymerase recruits alternative sigma factors as a means of switching on specific regulons. Most bacteria express a multiplicity of sigma factors. Two of these factors, sigma-70 (gene rpoD), generally known as the major or primary sigma factor, and sigma-54 (gene rpoN or ntrA) direct the transcription of a wide variety of genes. The other sigma factors, known as alternative sigma factors, are required for the transcription of specific subsets of genes. With regard to sequence similarity, sigma factors can be grouped into two classes, the sigma-54 and sigma-70 families. Sequence alignments of the sigma70 family members reveal four conserved regions that can be further divided into subregions eg. sub-region 2.2, which may be involved in the binding of the sigma factor to the core RNA polymerase; and sub-region 4.2, which seems to harbor a DNA-binding 'helix-turn-helix' motif involved in binding the conserved -35 region of promoters recognized by the major sigma factors , . This group of similar sigma-70 factors includes clades found in Bacilli (including the sporulation factors SigF:IPR014236 from INTERPRO and SigG:IPR014212 from INTERPRO as well as SigB:IPR014288 from INTERPRO), and the high GC Gram-positive bacteria (Actinobacteria) where a variable number of them are found depending on the lineage.; GO: 0003677 DNA binding, 0003700 transcription factor activity, 0016987 sigma factor activity, 0006352 transcription initiation, 0006355 regulation of transcription DNA-dependent.

>TIGR00721 tfx DNA-binding protein, Tfx family; InterPro: IPR004645 This is a family of Tfx DNA-binding proteins, which is restricted to the archaea

Homology among the members is strongest in the helix-turn-helix-containing N-terminal region. Tfx from Methanobacterium thermoautotrophicum is associated with the operon for molybdenum formyl-methanofuran dehydrogenase and binds a DNA sequence near its promoter.; GO: 0003677 DNA binding.

>TIGR02885 spore_sigF RNA polymerase sigma-F factor; InterPro: IPR014236 The bacterial core RNA polymerase complex, which consists of five subunits, is sufficient for transcription elongation and termination but is unable to initiate transcription

Transcription initiation from promoter elements requires a sixth, dissociable subunit called a sigma factor, which reversibly associates with the core RNA polymerase complex to form a holoenzyme . RNA polymerase recruits alternative sigma factors as a means of switching on specific regulons. Most bacteria express a multiplicity of sigma factors. Two of these factors, sigma-70 (gene rpoD), generally known as the major or primary sigma factor, and sigma-54 (gene rpoN or ntrA) direct the transcription of a wide variety of genes. The other sigma factors, known as alternative sigma factors, are required for the transcription of specific subsets of genes. With regard to sequence similarity, sigma factors can be grouped into two classes, the sigma-54 and sigma-70 families. Sequence alignments of the sigma70 family members reveal four conserved regions that can be further divided into subregions eg. sub-region 2.2, which may be involved in the binding of the sigma factor to the core RNA polymerase; and sub-region 4.2, which seems to harbor a DNA-binding 'helix-turn-helix' motif involved in binding the conserved -35 region of promoters recognized by the major sigma factors , . Members of this entry represent RNA polymerase sigma factor F. Within the Firmicutes, Sigma-F is specifically, and universally, a component of the endospore formation program, and is expressed in the forespore to turn on the expression of dozens of genes. It is closely related to sigma-G, which is also expressed in the forespore.; GO: 0003677 DNA binding, 0003700 transcription factor activity, 0016987 sigma factor activity, 0006352 transcription initiation, 0006355 regulation of transcription DNA-dependent.

This family consists of the N terminus of homeobox-containing transcription factor HNF-1. This region contains a dimerization sequence and an acidic region that may be involved in transcription activation. Mutations and the common Ala/Val 98 polymorphism in HNF-1 cause the type 3 form of maturity-onset diabetes of the young (MODY3).

Homologous Structures in PDB DatabaseDetected by PSI-BLAST, RPS-BLAST and HHsearch

>gi|157829815|pdb|1ADR|A Chain A, Determination Of The Nuclear Magnetic Resonance Structure Of The Dna-Binding Domain Of The P22 C2 Repressor (1-76) In Solution And Comparison With The Dna-Binding Domain Of The 434 Repressor Length = 76

>gi|157829815|pdb|1ADR|A Chain A, Determination Of The Nuclear Magnetic Resonance Structure Of The Dna-Binding Domain Of The P22 C2 Repressor (1-76) In Solution And Comparison With The Dna-Binding Domain Of The 434 Repressor Length = 76